The following relates generally to wireless communication, and more specifically to control flow enhancements for LTE-Unlicensed.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., an LIE system). A wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
In an LTE or LTE-Advanced (LTE-A) network, a base station and a UE may communicate over dedicated frequency spectrum that is licensed to the network operator. A licensed operator network (e.g., cellular network, etc.) may be known as a public land mobile network (PLMN). With increasing data traffic in cellular networks that use dedicated (e.g., licensed) radio frequency bands, offloading at least some data traffic to unlicensed or shared radio frequency spectrum may enhance data transmission capacity and efficient use of resources. Unlicensed and shared radio frequency spectrum may also provide service in areas where access to a dedicated radio frequency spectrum is unavailable. Unlicensed spectrum generally refers to spectrum available for use without a license and is typically subject to technical rules regarding access and transmitted power. Shared spectrum generally refers to spectrum that is available to devices associated with one of multiple operators.
A listen before talk (LBT) procedure may be used for contention resolution for access to shared frequency resources of licensed or unlicensed frequency spectrum without pre-coordinated resource allocation. An LBT procedure may include performing a clear channel assessment (CCA) procedure to determine whether a shared channel is available. When it is determined that the shared channel is available, a device may transmit a signal to reserve the channel before data transmissions. Other devices may monitor for the reservation signal to detect transmissions, and may also monitor the shared channel using energy detection to determine whether the shared channel is busy or free.
Operation using LTE signal waveforms over the shared radio frequency spectrum may be called LTE-Unlicensed (LTE-U) operation, and an LTE device supporting LTE-U operation may be called an LTE-U device. Operation using LTE/LTE-A carriers in unlicensed or shared frequency spectrum may be used in a standalone operation mode where an LTE/LTE-A carrier can be used as a primary cell for a UE. The LTE/LTE-A carrier may also be used in a licensed assisted access (LAA) mode where a UE is configured with a primary cell in a LTE/LTE-A carriers in unlicensed or shared frequency spectrum are configured as secondary cells in a carrier aggregation mode.
Because unlicensed cells (e.g., standalone or LAA) operating in unlicensed or shared frequency spectrum may be subject to LBT procedures, control flow management procedures designed around predetermined timing for dedicated spectrum may be subject to unpredictable timing variations. In addition, unlicensed or shared frequency spectrum may have additional restrictions that place limitations on transmission power or duration that can affect control flow management for unlicensed cells.